US20210108482A1 - Downhole plug with protective member - Google Patents
Downhole plug with protective member Download PDFInfo
- Publication number
- US20210108482A1 US20210108482A1 US16/982,102 US201916982102A US2021108482A1 US 20210108482 A1 US20210108482 A1 US 20210108482A1 US 201916982102 A US201916982102 A US 201916982102A US 2021108482 A1 US2021108482 A1 US 2021108482A1
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- US
- United States
- Prior art keywords
- elastic member
- mandrel
- plug
- pressure
- center element
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Images
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/12—Packers; Plugs
- E21B33/1208—Packers; Plugs characterised by the construction of the sealing or packing means
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/12—Packers; Plugs
- E21B33/128—Packers; Plugs with a member expanded radially by axial pressure
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/12—Packers; Plugs
- E21B33/129—Packers; Plugs with mechanical slips for hooking into the casing
- E21B33/1293—Packers; Plugs with mechanical slips for hooking into the casing with means for anchoring against downward and upward movement
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B2200/00—Special features related to earth drilling for obtaining oil, gas or water
- E21B2200/08—Down-hole devices using materials which decompose under well-bore conditions
Definitions
- the present invention relates to a plug and, in particular, to a downhole plug used to plug a wellbore.
- downhole plugs such as bridge plugs and frac plugs are known (e.g., Patent Document 1).
- One of the functions of the downhole plug is to plug the wellbore during hydraulic fracturing.
- a downhole plug is installed to a predetermined position of a wellbore, and the downhole plug is operated to be set to a well wall while an elastic member included in the downhole plug is deformed to plug the wellbore. Thereafter, a method is employed in which water is pumped from the ground into the wellbore, and hydraulic pressure is applied to a part closer to the ground than the downhole plug set to the well wall, thereby causing a crack in the subterranean formation through a perforation formed separately using an explosive or the like.
- Patent Document 2 discloses a downhole tool using a polymer composite material containing fibers as a material in order to improve hydraulic pressure resistance.
- an object of the present invention is to provide a downhole plug having excellent pressure resistance.
- the present invention provides a plug for plugging a wellbore, including: a cylindrical body; an annular elastic member configured to surround an outer peripheral surface of the cylindrical body and to be deformed under pressure; at least one protective member configured to surround the outer peripheral surface of the cylindrical body and to prevent at least a part of the elastic member from coming into contact with the cylindrical body; and a pair of pressure transmission means configured to sandwich the elastic member in an axial direction of the plug and to apply pressure to the elastic member in the axial direction to compress the elastic member.
- a ratio (b/a) of an axial length (b) of a part of the elastic member where the cylindrical body and the elastic member are in contact with each other, to a maximum axial length (a) of the elastic member in a cross section along the axial direction is less than 0.5.
- a downhole plug excellent in pressure resistance can be provided.
- FIG. 1 is a schematic view of a cross-section of a downhole plug at a predetermined position in a wellbore, according to Embodiment 1 of the present invention.
- FIG. 2 is a schematic view of a cross section of a downhole plug when subjected to hydraulic pressure at a wellbore, according to Embodiment 1 of the present invention.
- FIG. 3 is an enlarged schematic view of a part of a cross section of the downhole plug when subjected to hydraulic pressure at a wellbore, according to Embodiment 1 of the present invention.
- FIG. 4 is a schematic view of a cross section of a downhole plug at a predetermined position in a wellbore, according to Embodiment 2 of the present invention.
- FIG. 5 is a schematic view of a cross section of the downhole plug when subjected to hydraulic pressure at the wellbore, according to Embodiment 2 of the present invention.
- FIG. 6 is an enlarged schematic view of a part of a cross section of a downhole plug at a predetermined position in a wellbore, according to Embodiment 3 of the present invention.
- FIG. 7 is an enlarged schematic view of a part of a cross section of the downhole plug when subjected to hydraulic pressure at the wellbore, according to Embodiment 3 of the present invention.
- FIG. 8 is an enlarged schematic view of a part of a cross section of a downhole plug at a predetermined position in a wellbore, according to Embodiment 4 of the present invention.
- FIG. 9 is an enlarged schematic view of a part of a cross section of the downhole plug when subjected to hydraulic pressure at a wellbore, according to Embodiment 4 of the present invention.
- FIG. 10 is a schematic view illustrating a part of a cross section of a lip, according to Embodiment 5 of the present invention.
- a downhole plug (plug) according to Embodiment 1 of the present invention is a plug for plugging a wellbore.
- the downhole plug according to Embodiment 1 can have a first form in which the downhole plug is installed from the ground to a predetermined position in a wellbore, a second form in which the downhole plug is actuated and set to the wellbore, and a third form in which the downhole plug is subjected to hydraulic pressure.
- the first form corresponds to FIG. 1
- the third form corresponds to FIG. 2 .
- the second form is not illustrated.
- FIG. 1 is a schematic view of a cross section of a downhole plug in a first form in a predetermined position in a wellbore, according to the present Embodiment 1.
- FIG. 1 is a schematic view of a cross section of a downhole plug in a first form in a predetermined position in a wellbore, according to the present Embodiment 1.
- FIG. 1 is a schematic
- FIG. 2 is a schematic view of a cross section of a downhole plug in a third form under hydraulic pressure, according to the present Embodiment 1.
- FIG. 1 and FIG. 2 only one of the cross sections of the downhole plug that are symmetrical with respect to the axis (the dashed line in the drawings) is illustrated.
- FIG. 1 illustrates a situation where there is a gap between a well wall and the downhole plug in the well.
- the downhole plug 20 includes a mandrel (cylindrical body) 1 , a center element (elastic member) 2 , a lip (protective member) 3 , sockets (pressure transmission means) 4 a and 4 b , cones (pressure transmission means) 5 a and 5 b , and slips (pressure transmission means) 6 a and 6 b .
- the downhole plug 20 further includes equalizer rings (pressure transmission means) 7 a and 7 b , a load ring (pressure transmission means) 8 , and a bottom 9 .
- the downhole plug 20 has a cylindrical shape as a whole. In the following description, the term “axis” or “axial direction” simply refers to the axis or axial direction of the downhole plug 20 having a cylindrical shape as a whole.
- the mandrel 1 is a member for securing the strength of the downhole plug 20 , and is a hollow member that is disposed along the axis at the center of the downhole plug 20 .
- Various members for constituting the downhole plug 20 as a whole are deployed on the outer peripheral surface of the mandrel 1 .
- the material for forming the mandrel 1 examples include metal materials such as aluminum, steel, and stainless steel, fibers, wood, composite materials, and resins.
- the mandrel 1 may be formed of, for example, a composite material containing a reinforcing material such as carbon fiber, specifically, for example, a composite material containing a polymer such as an epoxy resin and a phenol resin.
- the mandrel 1 is preferably formed of a degradable resin or a degradable metal. This facilitates removal of the downhole plug 20 after performing well treatment using the downhole plug 20 .
- degradable resin or degradable metal means a resin or metal which can be degraded or embrittled to be easily disintegrated, by biodegradation or hydrolysis, dissolution in water or hydrocarbons in a wellbore, or any chemical method.
- the degradable resin examples include aliphatic polyesters based on hydroxycarboxylic acid such as polylactic acid (PLA) and polyglycolic acid (PGA), lactone-based aliphatic polyesters such as poly-caprolactone (PCL), diol-dicarboxylic acid-based aliphatic polyesters such as polyethylene succinate and polybutylene succinate, copolymers thereof, for example, such as glycolic acid-lactic acid copolymers, mixtures thereof, and further aliphatic polyesters in combination with aromatic components such as polyethylene adipate/terephthalate.
- aliphatic polyesters based on hydroxycarboxylic acid such as polylactic acid (PLA) and polyglycolic acid (PGA)
- lactone-based aliphatic polyesters such as poly-caprolactone (PCL)
- PCL poly-caprolactone
- diol-dicarboxylic acid-based aliphatic polyesters such as polyethylene succinate and polybutylene succinate,
- water-soluble resin examples include polyvinyl alcohol, polyvinyl butyral, polyvinyl formal, polyacrylamide (which may be N, N-substituted), polyacrylic acid, and polymethacrylic acid, and copolymers of monomers forming these resins, for example, such as ethylene-vinyl alcohol copolymer (EVOH) and acrylamide-acrylic acid-methacrylic acid interpolymer.
- EVOH ethylene-vinyl alcohol copolymer
- acrylamide-acrylic acid-methacrylic acid interpolymer examples of the water-soluble resin.
- degradable metal examples include, for example, metal alloys containing magnesium, aluminum, and calcium as main components.
- the center element 2 is an annular rubber member for filling the gap between the mandrel 1 and the well wall in the downhole plug 20 to plug the wellbore, and is deformed under pressure.
- the center element 2 is deployed around the outer peripheral surface of the mandrel 1 .
- the thickness, elasticity, inner diameter, outer diameter, or width in the axial direction, or the like of the center element 2 may be appropriately determined according to the size of the mandrel 1 , the pressure applied to the downhole plug 20 , or the like.
- the center element 2 is preferably formed of a material that does not lose the function of plugging the wellbore even under a high-temperature and high-pressure environment such as 100° C. and 30 MPa.
- preferable materials for forming the center element 2 include nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, and fluororubber, or the like.
- a degradable rubber such as aliphatic polyester rubber, polyurethane rubber, natural rubber, polyisoprene, acrylic rubber, aliphatic polyester rubber, polyester-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer can be used.
- the lip 3 is a member that prevents at least a part of the center element 2 from contacting the mandrel 1 to prevent damage to the mandrel 1 when the downhole plug 20 is used to plug a wellbore.
- the lip 3 since the lip 3 is inserted between the mandrel 1 and the center element 2 , at least a part of the center element 2 is prevented from contacting the mandrel 1 .
- the lip 3 may be at least partially inserted between the mandrel 1 and the center element 2 when pressure is applied to the downhole plug 20 .
- the mandrel 1 is a member for ensuring the strength of the downhole plug 20 .
- the strength of the mandrel 1 may not be sufficient for the force received from the center element 2 in some cases.
- the material forming the mandrel 1 is as described in the section of [Mandrel], but in general, a resin material has lower strength than a metal material, and among resin materials, a non-composite material containing no reinforcing material has lower strength.
- the pressure resistance of the downhole plug 20 is ensured because the downhole plug 20 includes the lip 3 .
- the lip 3 according to the present Embodiment 1 is an annular member deployed around the outer peripheral surface of the mandrel 1 , and is integrated with a cone 5 a described later. That is, the lip 3 is provided as a part of the cone 5 a .
- the inner peripheral edge of the cone 5 a in contact with the mandrel 1 protrudes toward the center element 2 , and the entire inner peripheral surface of the cone 5 a including the protruding part is in contact with the mandrel 1 .
- This protruding part corresponds to the lip 3 .
- the inner peripheral edge of the cone 5 a in contact with the mandrel 1 protrudes toward the center element 2 while being in contact with the mandrel 1 , thereby preventing a part of the center element 2 from contacting the mandrel 1 .
- the length of the lip 3 is designed based on the third form described later.
- the thickness of the lip 3 is not particularly limited as long as it does not prevent the lip 3 from moving between the center element 2 and the mandrel 1 when the cone 5 a moves toward the center element 2 under pressure.
- the thickness may be constant, or the thickness may change so as to decrease toward the tip of the lip 3 which is the protruding portion.
- the lip 3 may be designed such that the thickness on the side close to the cone 5 a is constant and the thickness on the side close to the tip decreases toward the tip.
- the material of the lip 3 is not particularly limited, and the material described as the material for forming the mandrel 1 can be used. Among them, for the same reason as the mandrel 1 , it is preferable that the lip 3 is formed of a degradable resin or a degradable metal.
- the pressure transmission elements constituting the pressure transmission means include sockets 4 a and 4 b , cones 5 a and 5 b , slips 6 a and 6 b , equalizer rings 7 a and 7 b , and a load ring 8 .
- the sockets 4 a and 4 b are arbitrary members that constitute pressure transmission means, and they retain the deformation of the center element 2 when the center element 2 is deformed under the axial pressure of the downhole plug 20 in the wellbore.
- the sockets 4 a and 4 b are annular members surrounding the outer peripheral surface of the mandrel 1 .
- the sockets 4 a and 4 b are mounted adjacent to one end of the center element 2 , and the sockets 4 a and 4 b contact each other.
- the socket 4 b is mounted in contact with the mandrel 1 but the socket 4 a is not mounted in contact with the mandrel 1 . That is, the sockets 4 a and 4 b have the same outer diameter, while the socket 4 a has a larger inner diameter.
- the socket 4 a is movably deployed on the socket 4 b.
- the material of the socket is not particularly limited, and the materials described above as the material for forming the mandrel 1 can be used. Among them, for the same reason as the mandrel 1 , it is preferable that the socket is formed of a degradable resin or a degradable metal. It is preferable that the socket 4 a is made of a material that can be deformed under pressure so as to expand its diameter.
- the cones 5 a and 5 b are members constituting a pressure transmission means, and transmit pressure directly and indirectly to the center element 2 , respectively.
- Cones 5 a and 5 b are mounted to surround the outer peripheral surface of the mandrel 1 .
- the cone 5 a is mounted adjacent the end of the center element 2 opposite to the end that the sockets 4 a and 4 b contact.
- the cone 5 b is mounted adjacent to the sockets 4 a and 4 b on the outer peripheral surface of the mandrel 1 on the side opposite to the center element 2 . That is, the sockets 4 a and 4 b are interposed between the cone 5 b and the center element 2 .
- the cone 5 a is a hollow conical member.
- the term “conical” means a cone, a truncated cone, or a combined shape of a cylinder therewith.
- the hollow shape is a shape along the outer peripheral surface of the mandrel, and is usually a cylindrical shape.
- the lip 3 is provided integrally with the cone 5 a .
- the cone 5 a has a shape in which the hollow conical solid having an outer diameter increasing from the end of the mandrel 1 toward the center element 2 is joined on the side of the center element 2 by a hollow cylindrical solid having a diameter smaller than the maximum diameter of the above conical solid.
- the cone 5 b is a hollow conical member and has a shape in which the outer diameter increases from the end of the mandrel 1 toward the center element 2 .
- the material of the cone is not particularly limited, and the materials described above as the material for forming the mandrel 1 can be used. Among them, for the same reason as the mandrel 1 , it is preferable that the cone is formed of a degradable resin or a degradable metal.
- the slips 6 a and 6 b are members constituting a pressure transmission means, and indirectly transmit pressure to the center element 2 .
- the slips 6 a and 6 b are deployed around the outer peripheral surface of the mandrel 1 and are in contact with the cones 5 a and 5 b , respectively.
- Each of the slips 6 a and 6 b is an annular member whose inner diameter decreases from the center element 2 side toward the end of the mandrel 1 .
- the material of the slip is not particularly limited, and the materials described above as the material for forming the mandrel 1 can be used.
- it is preferably formed of a degradable resin or a degradable metal.
- the equalizer rings 7 a and 7 b are arbitrary members constituting the pressure transmission means, and have a function of making the diameter expansion of the slips 6 a and 6 b uniform when shifting from the first form to the second form and from the second form to the third form, which will be described later, and also indirectly transmit pressure to the center element 2 .
- Equalizer rings 7 a and 7 b are mounted around the outer peripheral surface of the mandrel 1 and are in contact with slips 6 a and 6 b , respectively.
- the material of the equalizer ring is not particularly limited, and the material described as the material for forming the mandrel 1 can be used. Among them, for the same reason as the mandrel 1 , it is preferable that the equalizer ring is formed of a degradable resin or a degradable metal.
- the load ring 8 is a member constituting a pressure transmission means, and directly receives a pressure applied from the ground surface side of a wellbore and transmits the pressure to an adjacent member, thereby indirectly transmitting the pressure to the center element 2 .
- the load ring 8 is deployed around the outer peripheral surface of the mandrel 1 , and is in contact with the equalizer ring 7 a.
- the material of the load ring is not particularly limited, and the material described as the material for forming the mandrel 1 can be used. Among them, for the same reason as the mandrel 1 , it is preferable that the load ring is formed of a degradable resin or a degradable metal.
- a pair of pressure transmission means does not mean that the two pressure transmission means provided to sandwich the center element 2 have exactly the same configuration. That is, as long as they function as the pressure transmission means, the configuration included in each pressure transmission means may be different. Further, since the hydraulic pressure is normally received from only one side of the plug, the pressure transmission means on one side functions to transmit the pressure to the center element 2 , and the pressure transmission means on the other side functions to receive the center element 2 . As used herein, the term “pressure transmission means” will be used to include such a function.
- the downhole plug 20 may include a bottom 9 or the like as illustrated in FIG. 1 .
- the bottom 9 is attached so as to surround the outer peripheral surface of the mandrel 1 , but the arrangement of the bottom 9 may be appropriately determined as necessary.
- the material of the bottom 9 is not particularly limited as long as it can exhibit the respective functions, and the material described as the material for forming the mandrel 1 can be used. Among them, for the same reason as the mandrel 1 , it is preferable that the bottom 9 is formed of a degradable resin or a degradable metal.
- the second form of the downhole plug is one in which the downhole plug 20 is activated and set to the well.
- the downhole plug 20 is activated to expand the diameter of the center element 2 and bring it into contact with the well wall, thereby plugging the gap between the mandrel 1 and the well wall and expanding the diameter of the slips 6 a and 6 b .
- the downhole plug 20 is set in a predetermined position within the well by contacting the well wall.
- At least one of a pair of pressure transmission means moves in the axial direction of the mandrel 1 toward the center element 2 , so that the center element 2 is compressed in the axial direction, thereby increasing the outer diameter of the center element 2 .
- the outer peripheral surface of the center element 2 is brought into contact with the well wall 12 to plug the gap between the mandrel 1 and the well wall. This sets the downhole plug 20 to the well.
- the slips 6 a and 6 b slide on the inclined surfaces of the cones 5 a and 5 b , respectively, and the slips 6 a and 6 b contact the well wall 12 .
- pressure is transmitted to the center element 2 indirectly from the cone 5 b and directly from the cone 5 a and the sockets 4 a and 5 b , so that the center element 2 is compressed and deformed.
- the center element 2 When compressed, the center element 2 expands in a direction perpendicular to the axial direction of the mandrel 1 and contacts the well wall 12 , thereby setting the downhole plug 20 to the well. Additionally, when the center element 2 is deformed under pressure and the center element 2 is pressed against the sockets 4 a and 4 b , the socket 4 a is expanded in the diameter and slides on the inclined surface of the socket 4 b and contacts the well wall 12 . Thus, the downhole plug 20 changes into the second form.
- the third form of the downhole plug is the form when the downhole plug 20 is under hydraulic pressure.
- the third form of the downhole plug 20 will be described with reference to FIG. 2 .
- a frac ball 10 is inserted into the well and seated on a ball seat 13 of the downhole plug 20 to plug the hollow part of the mandrel 1 , which completes the plugging of the wellbore.
- water is injected from the mine mouth to apply hydraulic pressure from the mine mouth side toward the bottom side of the wellbore.
- the downhole plug 20 changes into a third form in which the mandrel 1 is moved toward the bottom side of the wellbore under pressure from the mine mouth side toward the bottom side of the wellbore.
- the mandrel 1 moves according to the hydraulic pressure.
- one of a pair of the pressure transmission means on the mine mouth side moves toward the bottom side of the wellbore due to the hydraulic pressure from the mine mouth side, thereby further compressing the center element 2 in some cases.
- the downhole plug 20 changes into the third form.
- the cone 5 a and the socket 4 sandwiching the center element are located closer to each other than in the first form. That is, in the third form, a part where the mandrel 1 and the center element 2 are in contact with each other is smaller than that in the first form. The part where the center element 2 and the mandrel 1 are in contact with each other will be described later.
- the center element 2 is in contact with the mandrel 1 , and the contact is prevented in part by the lip 3 .
- pressure is applied in the axial direction of the downhole plug 20 , and the distance between the cone 5 a having the lip 3 and the sockets 4 a and 4 b is reduced, whereby the center element 2 is compressed.
- the region where the center element 2 and the mandrel 1 are in contact with each other is different from that in the first form above.
- the ratio (b/a) of the total length (b) of the part where the mandrel 1 is in contact with the center element 2 to the maximum axial length (a) of the center element 2 when a pressure of 50 MPa is applied to the downhole plug 20 in the axial direction is less than 0.5.
- “when a pressure of 50 MPa is applied in the axial direction” means that a pressure is applied from one side to the other side in the axial direction of the downhole plug 20 . This is based on the assumption that pressure is applied from the mine mouth side of the downhole plug 20 toward the bottom side of the well when hydraulic pressure is applied from the mine mouth.
- the “maximum axial length (a) of the center element 2 ” is a width of the center element 2 in the axial direction in a cross section along the axial direction of the downhole plug 20 as illustrated in FIG. 2 . Namely, it is a length in the axial direction of the downhole plug 20 in the orthogonal projection of the center element 2 onto the mandrel 1 or the well wall 12 .
- a specific example will be described later in Embodiment 4, but when there are a plurality of center elements 2 , the sum of the axial length of each element is denoted by (a).
- the “length (b) of the axial part where the mandrel 1 and the center element 2 are in contact with each other” is the axial length of the part where the mandrel 1 and the center element 2 are in contact with each other in the cross section along the axial direction of the downhole plug 20 .
- the average value is used as (b).
- the ratio of (b) to (a) is less than 0.5 as described above, but the ratio may be preferably as small as possible, for example, preferably less than 0.25, more preferably less than 0.1, and most preferably 0.
- the ratio of (b) to (a) is smaller, that is, as the part where the mandrel 1 and the center element 2 are in contact with each other in the third form is smaller, the force applied from the center element 2 to the mandrel 1 , that is, the force for fastening the mandrel 1 is smaller, so that the breakage of the mandrel 1 can be more effectively prevented.
- the ratio (b/a) is less than 0.5, the lip 3 is present at the center part of the axial length of the center element 2 . Therefore, it is possible to prevent the center element 2 and the mandrel 1 from coming into contact with each other in a part where the force applied to the mandrel 1 is the largest, and it is possible to more reliably prevent damage to the mandrel 1 .
- the pressure applied to the downhole plug in the well during hydraulic fracturing is usually about 30 to 70 MPa. Therefore, if the ratio (b/a) when a pressure of 50 MPa is applied to the downhole plug 20 is less than 0.5, the ratio (b/a) can be less than 0.5 even in an actual use environment. Therefore, the excellent pressure resistance of the downhole plug 20 according to the present Embodiment 1 is exhibited in an actual use environment.
- FIG. 3 is an enlarged schematic view of a part of a cross section of a downhole plug 20 in a third form in which hydraulic pressure is received in a wellbore, according to a modified example of Embodiment 1. As illustrated in FIG.
- the tip of the lip 3 extending from the cone 5 a reaches the socket 4 and is in contact with the socket 4 .
- the force applied from the center element 2 to the mandrel 1 is further reduced, and damage to the mandrel 1 can be more reliably prevented.
- FIG. 4 is a schematic view of the cross section of a downhole plug at a predetermined position in a well, according to the present Embodiment 2.
- FIG. 5 is a schematic view of a cross section of a downhole plug when subjected to hydraulic pressure at a wellbore, according to Embodiment 2 of the present invention.
- FIG. 4 and FIG. 5 only one of the cross sections of the downhole plug that are symmetrical with respect to the axis (the dashed line in the drawings) is illustrated.
- the lip 3 is not integral with the cone 5 a , but is an annular member that exists separately from the cone 5 a .
- the lip 3 and the cone 5 a are separate bodies, they are provided on the outer peripheral surface of the mandrel 1 so as to be in contact with each other.
- the lip 3 is located on the side of the cone 5 a that is in contact with the center element 2 , and is in contact with the inner peripheral edge of the cone 5 a .
- the inner diameter of the lip 3 a is the same as the inner diameter of the cone 5 a
- the outer diameter of the lip 3 is smaller than the outer diameter of the cone 5 a .
- Embodiment 2 similarly to Embodiment 1, on the side of the cone 5 a of the center element 2 , the contact between the center element 2 and the mandrel 1 is prevented by the lip 3 . Since the lip 3 is in contact with the cone 5 a , when the cone 5 a moves toward the center element 2 , the lip 3 is also pushed and moved.
- the lip 3 and the cone 5 a may be in contact with each other, and may not be fixed to each other or may be fixed to each other by another means.
- the boundary between the lip 3 and the cone 5 a is not particularly limited, for example, as illustrated in FIGS. 4 and 5 , in the cross section of the downhole plug 21 , the boundary may be a perpendicular line drawn from the end of the center element 2 in contact with the cone 5 a to the mandrel 1 .
- a downhole plug according to Embodiment 3 of the present invention will be described with reference to FIGS. 6 and 7 .
- the first form of the downhole plug corresponds to FIG. 6
- the third form corresponds to FIG. 7 .
- FIG. 6 is an enlarged schematic view of a part of a cross section of the downhole plug at a predetermined position in a well, according to the present Embodiment 3.
- the sockets 4 a and 4 b are collectively illustrated as the socket 4 , and hereinafter also referred to as the socket 4 .
- the position of the lip 3 is not particularly limited as long as (b/a) is less than 0.5 when a pressure of 50 MPa is applied to the downhole plug.
- the lip 3 may be integrated with the socket 4 instead of being integrated with the cone 5 a.
- the lip 3 may be divided into two portions as illustrated in FIGS. 6 ( b ) and 6 ( b ′) and may be formed integrally with the socket 4 and with the cone 5 a respectively.
- the lip 3 integral with the socket 4 may be longer, or the lip 3 integral with the cone 5 a may be longer, or both may have the same length.
- the lip 3 may be independent of both the socket 4 and the cone 5 a and may not be in contact with either the socket 4 or the cone 5 a .
- the number of the lips 3 may be one or more.
- the lip 3 may be a combination of any of the forms described above.
- FIG. 7 is an enlarged schematic view of a part of a cross section of the downhole plug when hydraulic pressure is applied to a wellbore, according to Embodiment 3 of the present invention.
- the position of the lip 3 is not limited as long as the ratio of (b) to (a) illustrated in FIG. 7 is less than 0.5 when a pressure of 50 MPa is applied to the downhole plug.
- the lip 3 may be in contact with the socket 4 or the cone 5 a while being independent thereof.
- a downhole plug according to Embodiment 4 of the present invention will be described with reference to FIGS. 8 and 9 .
- the first form of the downhole plug corresponds to FIG. 8
- the third form corresponds to FIG. 9 .
- the downhole plug according to the present invention may have a form in which the center element 2 is divided into a plurality of portions and arranged along the axis of the mandrel 1 as illustrated in FIG. 8( a ) as long as (b/a) is less than 0.5 when a pressure of 50 MPa is applied to the downhole plug.
- (a) is the sum of the maximum lengths of the plurality of center elements.
- the thickness, elasticity, inner diameter, outer diameter, or width in the axial direction of the plurality of center elements may be the same or different.
- the length of the part where the mandrel and the center element are in contact with each other is preferably smaller than the maximum length of each center element.
- a partition 11 may be provided between the plurality of center elements.
- the partition 11 is not particularly limited as long as it is an annular member surrounding the mandrel 1 , and may be a part or all of the above-described pressure transmission means.
- the material of the partition 11 is not particularly limited, but is preferably formed of a degradable resin or a degradable metal from the viewpoint of facilitating removal of the downhole plug 20 after performing well treatment.
- FIG. 9 is an enlarged schematic view of a part of a cross section of a downhole plug when hydraulic pressure is applied to a wellbore, according to Embodiment 4 of the present invention.
- the partition 11 may or may not be provided between the plurality of center elements.
- the sum of the maximum axial lengths (a1) and (a2) of the plurality of center elements is defined as (a).
- the lip 3 is attached so as to surround the outer peripheral surface of the mandrel 1 , but the form does not have to be annular. That is, when a pressure of 50 MPa is applied to the downhole plug, in case that (b/a) is less than 0.5, the lip 3 may be divided into two or more portions at the outer periphery of the mandrel 1 .
- FIGS. 10( a ), ( b ) and ( c ) illustrate cross sections taken perpendicular to the axis of the lip 3
- FIGS. 10( a ) , (b′) and (c′) show side views along the axial direction of the lip.
- FIGS. 10( a ) , (a′), (b) and (b′) illustrate a lip 3 formed of two members of the lips 3 a and 3 b .
- FIGS. 10( c ) and 10 (c′) illustrate a lip 3 formed of three members of the lips 3 a , 3 b and 3 c .
- the lip 3 c has an annular shape, but may be divided into two or more portions on the outer periphery of the mandrel 1 as with the lips 3 a and 3 b.
- each split lip may be integral with the socket or the cone, or may be separate.
- the angle of the parting plane of the lip 3 is not limited and may not necessarily be parallel to the mandrel axis.
- the average value thereof is used as (b).
- a plug for plugging a wellbore includes: a cylindrical body; an elastic member with annular shape configured to surround an outer peripheral surface of the cylindrical body and to be deformed under pressure; at least one protective member configured to surround the outer peripheral surface of the cylindrical body and to prevent at least a part of the elastic member from coming into contact with the cylindrical body; and a pair of pressure transmission means configured to sandwich the elastic member in an axial direction of the plug and to apply pressure to the elastic member in the axial direction to compress the elastic member, where, when the elastic member is deformed by applying a pressure of 50 MPa to the plug in the axial direction, a ratio (b/a) of an axial length (b) of a part of the elastic member where the cylindrical body and the elastic member are in contact with each other, to a maximum axial length (a) of the elastic member in a cross section along the axial direction is less than 0.5.
- the elastic member sandwiched between a pair of pressure transmission means provided on the outer peripheral surface of the cylindrical body is compressed and deformed via a pair of pressure transmission means provided on the outer peripheral surface of the cylindrical body. At this time, at least a part of the elastic member is prevented from coming into contact with the cylindrical body by the protective member also provided on the outer peripheral surface of the cylindrical body.
- a ratio (b/a) of a length (b) in the axial direction of a part where the cylindrical body and the elastic member are in contact with each other to a maximum axial length (a) of the elastic member in a cross section along the axial direction is less than 0.5.
- a force is applied from the elastic member to the cylindrical body.
- the part where the elastic member and the cylindrical body are in contact with each other falls within the above range, the force applied to the cylindrical body is reduced. As a result, breakage of the cylindrical body can be prevented, and the plug has excellent pressure resistance.
- At least one of the protective members may be integrated with one of the pressure transmission elements constituting the pressure transmission means.
- At least one of the protective members may be independent of the pressure transmission means.
- a plurality of protective members are provided, and one of the plurality of protective members are integrated with one of the pressure transmission elements constituting one of the pair of pressure transmission means, and another one of the plurality of protective members is integrated with one of the pressure transmission elements constituting the other of the pair of pressure transmission means.
- one of the pressure transmission elements integrated with the protective member is a conical member which is in contact with an end of the elastic member and whose outer diameter increases from an end of the cylindrical body toward the elastic member.
- the protective member may be annular. According to this configuration, the cylindrical body of the plug can be more effectively prevented from coming into contact with the elastic member. Therefore, the plug is excellent in pressure resistance.
- the length (b) may be 0. According to this configuration, since the cylindrical body of the plug is not in contact with the elastic member, the plug is further excellent in pressure resistance.
- the downhole plug was placed in a metal tube having an inner diameter that is 1.1 times the outer diameter of the downhole plug, such that the axes of the downhole plug and the tube were parallel.
- the inside of the cylinder was maintained at 90° C., and a hydraulic pressure of 60 to 63 MPa was applied in the axial direction of the downhole plug to plug the cylinder. Then, the time period during which the tube was kept plugged was measured.
- Example 2 The same operation as in Example 1 was performed except that a downhole tool in which the axial length (a) of the center element and the axial length (b) of the part where the mandrel and the center element were in contact with each other in the cross section along the axial direction were equal to each other was used, the temperature was set to 90 to 93° C., and the hydraulic pressure was set to 50 to 53 MPa.
- Example 2 The same operation as in Example 1 was performed except that a downhole tool in which the axial length (a) of the center element and the axial length (b) of the part where the mandrel and the center element were in contact with each other in the cross section along the axial direction were equal to each other was used, the temperature was set to 90 to 93° C.
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Abstract
Description
- The present invention relates to a plug and, in particular, to a downhole plug used to plug a wellbore.
- Various tools called downhole tools have been developed to recover shale oil or shale gas. As one type of these downhole tools, downhole plugs such as bridge plugs and frac plugs are known (e.g., Patent Document 1). One of the functions of the downhole plug is to plug the wellbore during hydraulic fracturing.
- As a method of hydraulic fracturing, for example, a downhole plug is installed to a predetermined position of a wellbore, and the downhole plug is operated to be set to a well wall while an elastic member included in the downhole plug is deformed to plug the wellbore. Thereafter, a method is employed in which water is pumped from the ground into the wellbore, and hydraulic pressure is applied to a part closer to the ground than the downhole plug set to the well wall, thereby causing a crack in the subterranean formation through a perforation formed separately using an explosive or the like.
- Therefore, downhole plugs are required to withstand high hydraulic pressure from the ground and keep the wellbore plugged while being set to the well wall. On the other hand,
Patent Document 2 discloses a downhole tool using a polymer composite material containing fibers as a material in order to improve hydraulic pressure resistance. -
- Patent Document 1: US 2017/234,103
- Patent Document 2: US 2010/288,488
- However, when high hydraulic pressure is applied after the elastic member of the downhole plug is deformed to plug the wellbore, there is a problem that other components constituting the downhole plug are damaged due to unintended deformation of the elastic member, and that the pressure resistance of the downhole plug is reduced.
- Therefore, an object of the present invention is to provide a downhole plug having excellent pressure resistance.
- In order to solve the above problems, the present invention provides a plug for plugging a wellbore, including: a cylindrical body; an annular elastic member configured to surround an outer peripheral surface of the cylindrical body and to be deformed under pressure; at least one protective member configured to surround the outer peripheral surface of the cylindrical body and to prevent at least a part of the elastic member from coming into contact with the cylindrical body; and a pair of pressure transmission means configured to sandwich the elastic member in an axial direction of the plug and to apply pressure to the elastic member in the axial direction to compress the elastic member.
- When the elastic member is deformed by applying a pressure of 50 MPa to the plug in the axial direction, a ratio (b/a) of an axial length (b) of a part of the elastic member where the cylindrical body and the elastic member are in contact with each other, to a maximum axial length (a) of the elastic member in a cross section along the axial direction is less than 0.5.
- According to the present invention, a downhole plug excellent in pressure resistance can be provided.
-
FIG. 1 is a schematic view of a cross-section of a downhole plug at a predetermined position in a wellbore, according toEmbodiment 1 of the present invention. -
FIG. 2 is a schematic view of a cross section of a downhole plug when subjected to hydraulic pressure at a wellbore, according toEmbodiment 1 of the present invention. -
FIG. 3 is an enlarged schematic view of a part of a cross section of the downhole plug when subjected to hydraulic pressure at a wellbore, according toEmbodiment 1 of the present invention. -
FIG. 4 is a schematic view of a cross section of a downhole plug at a predetermined position in a wellbore, according toEmbodiment 2 of the present invention. -
FIG. 5 is a schematic view of a cross section of the downhole plug when subjected to hydraulic pressure at the wellbore, according toEmbodiment 2 of the present invention. -
FIG. 6 is an enlarged schematic view of a part of a cross section of a downhole plug at a predetermined position in a wellbore, according toEmbodiment 3 of the present invention. -
FIG. 7 is an enlarged schematic view of a part of a cross section of the downhole plug when subjected to hydraulic pressure at the wellbore, according toEmbodiment 3 of the present invention. -
FIG. 8 is an enlarged schematic view of a part of a cross section of a downhole plug at a predetermined position in a wellbore, according toEmbodiment 4 of the present invention. -
FIG. 9 is an enlarged schematic view of a part of a cross section of the downhole plug when subjected to hydraulic pressure at a wellbore, according toEmbodiment 4 of the present invention. -
FIG. 10 is a schematic view illustrating a part of a cross section of a lip, according to Embodiment 5 of the present invention. - A downhole plug (plug) according to
Embodiment 1 of the present invention is a plug for plugging a wellbore. The downhole plug according toEmbodiment 1 can have a first form in which the downhole plug is installed from the ground to a predetermined position in a wellbore, a second form in which the downhole plug is actuated and set to the wellbore, and a third form in which the downhole plug is subjected to hydraulic pressure. The first form corresponds toFIG. 1 , and the third form corresponds toFIG. 2 . The second form is not illustrated.FIG. 1 is a schematic view of a cross section of a downhole plug in a first form in a predetermined position in a wellbore, according to thepresent Embodiment 1.FIG. 2 is a schematic view of a cross section of a downhole plug in a third form under hydraulic pressure, according to thepresent Embodiment 1. InFIG. 1 andFIG. 2 , only one of the cross sections of the downhole plug that are symmetrical with respect to the axis (the dashed line in the drawings) is illustrated. - Hereinafter, the downhole plug according to the
present Embodiment 1 will be described in detail with reference toFIGS. 1 and 2 . - A first form of the downhole plug will be described with reference to
FIG. 1 .FIG. 1 illustrates a situation where there is a gap between a well wall and the downhole plug in the well. - As illustrated in
FIG. 1 , the downhole plug 20 includes a mandrel (cylindrical body) 1, a center element (elastic member) 2, a lip (protective member) 3, sockets (pressure transmission means) 4 a and 4 b, cones (pressure transmission means) 5 a and 5 b, and slips (pressure transmission means) 6 a and 6 b. The downhole plug 20 further includes equalizer rings (pressure transmission means) 7 a and 7 b, a load ring (pressure transmission means) 8, and abottom 9. The downhole plug 20 has a cylindrical shape as a whole. In the following description, the term “axis” or “axial direction” simply refers to the axis or axial direction of the downhole plug 20 having a cylindrical shape as a whole. - Hereinafter, each member will be described in detail.
- The
mandrel 1 is a member for securing the strength of the downhole plug 20, and is a hollow member that is disposed along the axis at the center of the downhole plug 20. Various members for constituting the downhole plug 20 as a whole are deployed on the outer peripheral surface of themandrel 1. - Examples of the material for forming the
mandrel 1 include metal materials such as aluminum, steel, and stainless steel, fibers, wood, composite materials, and resins. Themandrel 1 may be formed of, for example, a composite material containing a reinforcing material such as carbon fiber, specifically, for example, a composite material containing a polymer such as an epoxy resin and a phenol resin. - In particular, the
mandrel 1 is preferably formed of a degradable resin or a degradable metal. This facilitates removal of the downhole plug 20 after performing well treatment using the downhole plug 20. - In the present specification, the term “degradable resin or degradable metal” means a resin or metal which can be degraded or embrittled to be easily disintegrated, by biodegradation or hydrolysis, dissolution in water or hydrocarbons in a wellbore, or any chemical method.
- Examples of the degradable resin include aliphatic polyesters based on hydroxycarboxylic acid such as polylactic acid (PLA) and polyglycolic acid (PGA), lactone-based aliphatic polyesters such as poly-caprolactone (PCL), diol-dicarboxylic acid-based aliphatic polyesters such as polyethylene succinate and polybutylene succinate, copolymers thereof, for example, such as glycolic acid-lactic acid copolymers, mixtures thereof, and further aliphatic polyesters in combination with aromatic components such as polyethylene adipate/terephthalate.
- Examples of the water-soluble resin include polyvinyl alcohol, polyvinyl butyral, polyvinyl formal, polyacrylamide (which may be N, N-substituted), polyacrylic acid, and polymethacrylic acid, and copolymers of monomers forming these resins, for example, such as ethylene-vinyl alcohol copolymer (EVOH) and acrylamide-acrylic acid-methacrylic acid interpolymer.
- Examples of the degradable metal include, for example, metal alloys containing magnesium, aluminum, and calcium as main components.
- The
center element 2 is an annular rubber member for filling the gap between themandrel 1 and the well wall in the downhole plug 20 to plug the wellbore, and is deformed under pressure. Thecenter element 2 is deployed around the outer peripheral surface of themandrel 1. - The thickness, elasticity, inner diameter, outer diameter, or width in the axial direction, or the like of the
center element 2 may be appropriately determined according to the size of themandrel 1, the pressure applied to the downhole plug 20, or the like. - The
center element 2 is preferably formed of a material that does not lose the function of plugging the wellbore even under a high-temperature and high-pressure environment such as 100° C. and 30 MPa. Examples of preferable materials for forming thecenter element 2 include nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, and fluororubber, or the like. Moreover, a degradable rubber such as aliphatic polyester rubber, polyurethane rubber, natural rubber, polyisoprene, acrylic rubber, aliphatic polyester rubber, polyester-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer can be used. - The
lip 3 is a member that prevents at least a part of thecenter element 2 from contacting themandrel 1 to prevent damage to themandrel 1 when the downhole plug 20 is used to plug a wellbore. In thepresent Embodiment 1, since thelip 3 is inserted between themandrel 1 and thecenter element 2, at least a part of thecenter element 2 is prevented from contacting themandrel 1. Thelip 3 may be at least partially inserted between themandrel 1 and thecenter element 2 when pressure is applied to the downhole plug 20. - As will be described in detail later, when the downhole plug 20 receives hydraulic pressure and the
center element 2 is compressed, a force is applied to themandrel 1 from thecenter element 2. In the third form after thecenter element 2 is deformed under the hydraulic pressure, since the part of thecenter element 2 in contact with themandrel 1 is reduced by thelip 3, it is possible to reduce the force received by themandrel 1 from thecenter element 2. This can prevent damage to themandrel 1. Since the damage of themandrel 1 is prevented by thelip 3, a downhole plug having excellent pressure resistance can be provided. - As described above, the
mandrel 1 is a member for ensuring the strength of the downhole plug 20. However, depending on the material or thickness of themandrel 1, the strength of themandrel 1 may not be sufficient for the force received from thecenter element 2 in some cases. The material forming themandrel 1 is as described in the section of [Mandrel], but in general, a resin material has lower strength than a metal material, and among resin materials, a non-composite material containing no reinforcing material has lower strength. Thus, even when the strength of themandrel 1 is not sufficient, the pressure resistance of the downhole plug 20 is ensured because the downhole plug 20 includes thelip 3. - The
lip 3 according to thepresent Embodiment 1 is an annular member deployed around the outer peripheral surface of themandrel 1, and is integrated with acone 5 a described later. That is, thelip 3 is provided as a part of thecone 5 a. Specifically, the inner peripheral edge of thecone 5 a in contact with themandrel 1 protrudes toward thecenter element 2, and the entire inner peripheral surface of thecone 5 a including the protruding part is in contact with themandrel 1. This protruding part corresponds to thelip 3. The inner peripheral edge of thecone 5 a in contact with themandrel 1 protrudes toward thecenter element 2 while being in contact with themandrel 1, thereby preventing a part of thecenter element 2 from contacting themandrel 1. - The length of the
lip 3 is designed based on the third form described later. - The thickness of the
lip 3 is not particularly limited as long as it does not prevent thelip 3 from moving between thecenter element 2 and themandrel 1 when thecone 5 a moves toward thecenter element 2 under pressure. In addition, the thickness may be constant, or the thickness may change so as to decrease toward the tip of thelip 3 which is the protruding portion. Alternatively, thelip 3 may be designed such that the thickness on the side close to thecone 5 a is constant and the thickness on the side close to the tip decreases toward the tip. - The material of the
lip 3 is not particularly limited, and the material described as the material for forming themandrel 1 can be used. Among them, for the same reason as themandrel 1, it is preferable that thelip 3 is formed of a degradable resin or a degradable metal. - The pressure transmission elements constituting the pressure transmission means include
sockets cones load ring 8. - The
sockets center element 2 when thecenter element 2 is deformed under the axial pressure of the downhole plug 20 in the wellbore. - The
sockets mandrel 1. Thesockets center element 2, and thesockets socket 4 b is mounted in contact with themandrel 1 but thesocket 4 a is not mounted in contact with themandrel 1. That is, thesockets socket 4 a has a larger inner diameter. Thesocket 4 a is movably deployed on thesocket 4 b. - The material of the socket is not particularly limited, and the materials described above as the material for forming the
mandrel 1 can be used. Among them, for the same reason as themandrel 1, it is preferable that the socket is formed of a degradable resin or a degradable metal. It is preferable that thesocket 4 a is made of a material that can be deformed under pressure so as to expand its diameter. - The
cones center element 2, respectively. -
Cones mandrel 1. Thecone 5 a is mounted adjacent the end of thecenter element 2 opposite to the end that thesockets cone 5 b is mounted adjacent to thesockets mandrel 1 on the side opposite to thecenter element 2. That is, thesockets cone 5 b and thecenter element 2. - The
cone 5 a is a hollow conical member. In the present specification, the term “conical” means a cone, a truncated cone, or a combined shape of a cylinder therewith. The hollow shape is a shape along the outer peripheral surface of the mandrel, and is usually a cylindrical shape. - As described above, in the present Embodiment, the
lip 3 is provided integrally with thecone 5 a. Accordingly, thecone 5 a has a shape in which the hollow conical solid having an outer diameter increasing from the end of themandrel 1 toward thecenter element 2 is joined on the side of thecenter element 2 by a hollow cylindrical solid having a diameter smaller than the maximum diameter of the above conical solid. - On the other hand, the
cone 5 b is a hollow conical member and has a shape in which the outer diameter increases from the end of themandrel 1 toward thecenter element 2. - The material of the cone is not particularly limited, and the materials described above as the material for forming the
mandrel 1 can be used. Among them, for the same reason as themandrel 1, it is preferable that the cone is formed of a degradable resin or a degradable metal. - The
slips center element 2. Theslips mandrel 1 and are in contact with thecones - Each of the
slips center element 2 side toward the end of themandrel 1. - The material of the slip is not particularly limited, and the materials described above as the material for forming the
mandrel 1 can be used. In particular, for the same reason as themandrel 1, it is preferably formed of a degradable resin or a degradable metal. - The equalizer rings 7 a and 7 b are arbitrary members constituting the pressure transmission means, and have a function of making the diameter expansion of the
slips center element 2. Equalizer rings 7 a and 7 b are mounted around the outer peripheral surface of themandrel 1 and are in contact withslips - The material of the equalizer ring is not particularly limited, and the material described as the material for forming the
mandrel 1 can be used. Among them, for the same reason as themandrel 1, it is preferable that the equalizer ring is formed of a degradable resin or a degradable metal. - The
load ring 8 is a member constituting a pressure transmission means, and directly receives a pressure applied from the ground surface side of a wellbore and transmits the pressure to an adjacent member, thereby indirectly transmitting the pressure to thecenter element 2. Theload ring 8 is deployed around the outer peripheral surface of themandrel 1, and is in contact with theequalizer ring 7 a. - The material of the load ring is not particularly limited, and the material described as the material for forming the
mandrel 1 can be used. Among them, for the same reason as themandrel 1, it is preferable that the load ring is formed of a degradable resin or a degradable metal. - In the present specification, the term “a pair of pressure transmission means” does not mean that the two pressure transmission means provided to sandwich the
center element 2 have exactly the same configuration. That is, as long as they function as the pressure transmission means, the configuration included in each pressure transmission means may be different. Further, since the hydraulic pressure is normally received from only one side of the plug, the pressure transmission means on one side functions to transmit the pressure to thecenter element 2, and the pressure transmission means on the other side functions to receive thecenter element 2. As used herein, the term “pressure transmission means” will be used to include such a function. - In addition to the above-described members, the downhole plug 20 may include a bottom 9 or the like as illustrated in
FIG. 1 . Thebottom 9 is attached so as to surround the outer peripheral surface of themandrel 1, but the arrangement of the bottom 9 may be appropriately determined as necessary. In addition, the material of thebottom 9 is not particularly limited as long as it can exhibit the respective functions, and the material described as the material for forming themandrel 1 can be used. Among them, for the same reason as themandrel 1, it is preferable that thebottom 9 is formed of a degradable resin or a degradable metal. - The second form of the downhole plug is one in which the downhole plug 20 is activated and set to the well.
- After the downhole plug 20 is disposed at a predetermined position in the well, the downhole plug 20 is activated to expand the diameter of the
center element 2 and bring it into contact with the well wall, thereby plugging the gap between themandrel 1 and the well wall and expanding the diameter of theslips FIG. 1 illustrating the first form. - When the downhole plug 20 is activated in the well, at least one of a pair of pressure transmission means moves in the axial direction of the
mandrel 1 toward thecenter element 2, so that thecenter element 2 is compressed in the axial direction, thereby increasing the outer diameter of thecenter element 2. As a result, the outer peripheral surface of thecenter element 2 is brought into contact with thewell wall 12 to plug the gap between themandrel 1 and the well wall. This sets the downhole plug 20 to the well. - In particular, when the downhole plug 20 is activated, the
slips cones slips well wall 12. At the same time, pressure is transmitted to thecenter element 2 indirectly from thecone 5 b and directly from thecone 5 a and thesockets center element 2 is compressed and deformed. - When compressed, the
center element 2 expands in a direction perpendicular to the axial direction of themandrel 1 and contacts thewell wall 12, thereby setting the downhole plug 20 to the well. Additionally, when thecenter element 2 is deformed under pressure and thecenter element 2 is pressed against thesockets socket 4 a is expanded in the diameter and slides on the inclined surface of thesocket 4 b and contacts thewell wall 12. Thus, the downhole plug 20 changes into the second form. - The third form of the downhole plug is the form when the downhole plug 20 is under hydraulic pressure. Hereinafter, the third form of the downhole plug 20 will be described with reference to
FIG. 2 . - After the downhole plug 20 is set at a predetermined position in the well, a
frac ball 10 is inserted into the well and seated on aball seat 13 of the downhole plug 20 to plug the hollow part of themandrel 1, which completes the plugging of the wellbore. Thereafter, water is injected from the mine mouth to apply hydraulic pressure from the mine mouth side toward the bottom side of the wellbore. The downhole plug 20 changes into a third form in which themandrel 1 is moved toward the bottom side of the wellbore under pressure from the mine mouth side toward the bottom side of the wellbore. - When hydraulic pressure is applied to the downhole plug 20 of the second form from the mine mouth side, the
mandrel 1 moves according to the hydraulic pressure. At this time, one of a pair of the pressure transmission means on the mine mouth side moves toward the bottom side of the wellbore due to the hydraulic pressure from the mine mouth side, thereby further compressing thecenter element 2 in some cases. Thus, the downhole plug 20 changes into the third form. - Further, in the third form, the
cone 5 a and thesocket 4 sandwiching the center element are located closer to each other than in the first form. That is, in the third form, a part where themandrel 1 and thecenter element 2 are in contact with each other is smaller than that in the first form. The part where thecenter element 2 and themandrel 1 are in contact with each other will be described later. - As described above, the
center element 2 is in contact with themandrel 1, and the contact is prevented in part by thelip 3. In the third form, pressure is applied in the axial direction of the downhole plug 20, and the distance between thecone 5 a having thelip 3 and thesockets center element 2 is compressed. Thus, in the third form, the region where thecenter element 2 and themandrel 1 are in contact with each other is different from that in the first form above. Specifically describing the contact part between thecenter element 2 and themandrel 1 in the third form, in the third form of the downhole plug 20, the ratio (b/a) of the total length (b) of the part where themandrel 1 is in contact with thecenter element 2 to the maximum axial length (a) of thecenter element 2 when a pressure of 50 MPa is applied to the downhole plug 20 in the axial direction is less than 0.5. - Here, “when a pressure of 50 MPa is applied in the axial direction” means that a pressure is applied from one side to the other side in the axial direction of the downhole plug 20. This is based on the assumption that pressure is applied from the mine mouth side of the downhole plug 20 toward the bottom side of the well when hydraulic pressure is applied from the mine mouth.
- Here, the “maximum axial length (a) of the
center element 2” is a width of thecenter element 2 in the axial direction in a cross section along the axial direction of the downhole plug 20 as illustrated inFIG. 2 . Namely, it is a length in the axial direction of the downhole plug 20 in the orthogonal projection of thecenter element 2 onto themandrel 1 or thewell wall 12. A specific example will be described later inEmbodiment 4, but when there are a plurality ofcenter elements 2, the sum of the axial length of each element is denoted by (a). - As illustrated in
FIG. 2 , the “length (b) of the axial part where themandrel 1 and thecenter element 2 are in contact with each other” is the axial length of the part where themandrel 1 and thecenter element 2 are in contact with each other in the cross section along the axial direction of the downhole plug 20. When the length of the part of the outer periphery of themandrel 1 in contact with thecenter element 2 is not constant, the average value is used as (b). Although a specific example will be described later inEmbodiment 3, when there are a plurality of parts where themandrel 1 and thecenter element 2 are in contact with each other in a certain cross section, the sum of the axial lengths of the plurality of portions is defined as (b). - The ratio of (b) to (a) is less than 0.5 as described above, but the ratio may be preferably as small as possible, for example, preferably less than 0.25, more preferably less than 0.1, and most preferably 0. A ratio of (b) to (a) of 0 means that (b)=0.
- As the ratio of (b) to (a) is smaller, that is, as the part where the
mandrel 1 and thecenter element 2 are in contact with each other in the third form is smaller, the force applied from thecenter element 2 to themandrel 1, that is, the force for fastening themandrel 1 is smaller, so that the breakage of themandrel 1 can be more effectively prevented. In addition, when thecenter element 2 is compressed and deformed, it is presumed that the deformation is largest in the vicinity of the center part in the axial direction of thecenter element 2 and the force applied to themandrel 1 is strongest. When the ratio (b/a) is less than 0.5, thelip 3 is present at the center part of the axial length of thecenter element 2. Therefore, it is possible to prevent thecenter element 2 and themandrel 1 from coming into contact with each other in a part where the force applied to themandrel 1 is the largest, and it is possible to more reliably prevent damage to themandrel 1. - The pressure applied to the downhole plug in the well during hydraulic fracturing is usually about 30 to 70 MPa. Therefore, if the ratio (b/a) when a pressure of 50 MPa is applied to the downhole plug 20 is less than 0.5, the ratio (b/a) can be less than 0.5 even in an actual use environment. Therefore, the excellent pressure resistance of the downhole plug 20 according to the
present Embodiment 1 is exhibited in an actual use environment. - A modified example of the
present Embodiment 1 will be described. In the downhole plug 20 described above, also in the third form, thecenter element 2 and themandrel 1 are in contact with each other with a predetermined length (that is, b>0). However, by increasing the axial length of thelip 3, in the third form, the contact of thecenter element 2 with themandrel 1 may be completely blocked by thelip 3, that is, (b)=0.FIG. 3 illustrates a case where (b)=0.FIG. 3 is an enlarged schematic view of a part of a cross section of a downhole plug 20 in a third form in which hydraulic pressure is received in a wellbore, according to a modified example ofEmbodiment 1. As illustrated inFIG. 3 , in the third form of the downhole plug 20 according to the modified example, the tip of thelip 3 extending from thecone 5 a reaches thesocket 4 and is in contact with thesocket 4. As a result, thelip 3 sinks into the entire inner peripheral surface of thecenter element 2 that is in contact with themandrel 1 in the first form. Therefore, the contact of thecenter element 2 with themandrel 1 is completely blocked by thelip 3, and there is no shaft part where themandrel 1 is in contact with the center element 2 (that is, (b)=0). As a result, the force applied from thecenter element 2 to themandrel 1 is further reduced, and damage to themandrel 1 can be more reliably prevented. - Further, when (b)=0, since the tip of the
lip 3 reaches thesocket 4, thelip 3 also functions as a rod. Therefore, excessive deformation of thecenter element 2 can be prevented, and the pressure resistance in the axial direction is improved. - In the subsequent embodiments, members having the same functions as those described in the section of [Embodiment 1] are denoted by the same reference numerals, and description thereof will not be repeated.
- A downhole plug according to
Embodiment 2 of the present invention will be described with reference toFIGS. 4 and 5 . The first form of the downhole plug corresponds toFIG. 4 , and the third form corresponds toFIG. 5 .FIG. 4 is a schematic view of the cross section of a downhole plug at a predetermined position in a well, according to thepresent Embodiment 2.FIG. 5 is a schematic view of a cross section of a downhole plug when subjected to hydraulic pressure at a wellbore, according toEmbodiment 2 of the present invention. InFIG. 4 andFIG. 5 , only one of the cross sections of the downhole plug that are symmetrical with respect to the axis (the dashed line in the drawings) is illustrated. - In the
downhole plug 21 according toEmbodiment 2, as illustrated inFIGS. 4 and 5 , thelip 3 is not integral with thecone 5 a, but is an annular member that exists separately from thecone 5 a. Although thelip 3 and thecone 5 a are separate bodies, they are provided on the outer peripheral surface of themandrel 1 so as to be in contact with each other. Specifically, thelip 3 is located on the side of thecone 5 a that is in contact with thecenter element 2, and is in contact with the inner peripheral edge of thecone 5 a. The inner diameter of thelip 3 a is the same as the inner diameter of thecone 5 a, and the outer diameter of thelip 3 is smaller than the outer diameter of thecone 5 a. Therefore, also inEmbodiment 2, similarly toEmbodiment 1, on the side of thecone 5 a of thecenter element 2, the contact between thecenter element 2 and themandrel 1 is prevented by thelip 3. Since thelip 3 is in contact with thecone 5 a, when thecone 5 a moves toward thecenter element 2, thelip 3 is also pushed and moved. - The
lip 3 and thecone 5 a may be in contact with each other, and may not be fixed to each other or may be fixed to each other by another means. - Although the boundary between the
lip 3 and thecone 5 a is not particularly limited, for example, as illustrated inFIGS. 4 and 5 , in the cross section of thedownhole plug 21, the boundary may be a perpendicular line drawn from the end of thecenter element 2 in contact with thecone 5 a to themandrel 1. - A downhole plug according to
Embodiment 3 of the present invention will be described with reference toFIGS. 6 and 7 . The first form of the downhole plug corresponds toFIG. 6 , and the third form corresponds toFIG. 7 . -
FIG. 6 is an enlarged schematic view of a part of a cross section of the downhole plug at a predetermined position in a well, according to thepresent Embodiment 3. In the description with reference toFIGS. 6 and 7 , since there is no need to distinguish between thesocket 4 a and thesocket 4 b, thesockets socket 4, and hereinafter also referred to as thesocket 4. - The position of the
lip 3 is not particularly limited as long as (b/a) is less than 0.5 when a pressure of 50 MPa is applied to the downhole plug. - Specifically, as illustrated in
FIG. 6(a) , thelip 3 may be integrated with thesocket 4 instead of being integrated with thecone 5 a. - Alternatively, the
lip 3 may be divided into two portions as illustrated inFIGS. 6 (b) and 6(b′) and may be formed integrally with thesocket 4 and with thecone 5 a respectively. With regard to the twoseparate lips 3, thelip 3 integral with thesocket 4 may be longer, or thelip 3 integral with thecone 5 a may be longer, or both may have the same length. - As illustrated in
FIG. 6(c) , thelip 3 may be independent of both thesocket 4 and thecone 5 a and may not be in contact with either thesocket 4 or thecone 5 a. Here, the number of thelips 3 may be one or more. - Further, the
lip 3 may be a combination of any of the forms described above. -
FIG. 7 is an enlarged schematic view of a part of a cross section of the downhole plug when hydraulic pressure is applied to a wellbore, according toEmbodiment 3 of the present invention. - As described above, the position of the
lip 3 is not limited as long as the ratio of (b) to (a) illustrated inFIG. 7 is less than 0.5 when a pressure of 50 MPa is applied to the downhole plug. Although each ofFIG. 7 illustrates a form in which (b/a) is larger than 0, the case of (b)=0 illustrated inFIG. 3 is preferable. - As illustrated in
FIG. 7(c) , when there are a plurality of parts where themandrel 1 and thecenter element 2 are in contact with each other, the sum of the axial lengths (b1) and (b2) of the plurality of parts is defined as (b). - In the case where at least one of the
lips 3 described in the section of [Embodiment 3] is integrated with thesocket 4 or thecone 5 a, as described in the section of [Embodiment 2], thelip 3 may be in contact with thesocket 4 or thecone 5 a while being independent thereof. - A downhole plug according to
Embodiment 4 of the present invention will be described with reference toFIGS. 8 and 9 . The first form of the downhole plug corresponds toFIG. 8 , and the third form corresponds toFIG. 9 . - The downhole plug according to the present invention may have a form in which the
center element 2 is divided into a plurality of portions and arranged along the axis of themandrel 1 as illustrated inFIG. 8(a) as long as (b/a) is less than 0.5 when a pressure of 50 MPa is applied to the downhole plug. In addition, (a) is the sum of the maximum lengths of the plurality of center elements. - Here, the thickness, elasticity, inner diameter, outer diameter, or width in the axial direction of the plurality of center elements may be the same or different. However, from the viewpoint of preventing breakage of the mandrel, in each of the plurality of center elements, the length of the part where the mandrel and the center element are in contact with each other is preferably smaller than the maximum length of each center element.
- As illustrated in
FIG. 8(b) , apartition 11 may be provided between the plurality of center elements. Thepartition 11 is not particularly limited as long as it is an annular member surrounding themandrel 1, and may be a part or all of the above-described pressure transmission means. The material of thepartition 11 is not particularly limited, but is preferably formed of a degradable resin or a degradable metal from the viewpoint of facilitating removal of the downhole plug 20 after performing well treatment. -
FIG. 9 is an enlarged schematic view of a part of a cross section of a downhole plug when hydraulic pressure is applied to a wellbore, according toEmbodiment 4 of the present invention. - As described above, when a pressure of 50 MPa is applied to the downhole plug, in case that the ratio of (b) to (a) illustrated in
FIG. 9 is less than 0.5, thepartition 11 may or may not be provided between the plurality of center elements. Although each ofFIG. 9 illustrates a mode in which (b/a) is larger than 0, the case of (b)=0 illustrated inFIG. 3 is preferable. - As illustrated in
FIG. 9(b) , in the case where a plurality of center elements are present, the sum of the maximum axial lengths (a1) and (a2) of the plurality of center elements is defined as (a). - The
lip 3 is attached so as to surround the outer peripheral surface of themandrel 1, but the form does not have to be annular. That is, when a pressure of 50 MPa is applied to the downhole plug, in case that (b/a) is less than 0.5, thelip 3 may be divided into two or more portions at the outer periphery of themandrel 1. - This will be described with reference to
FIG. 10 .FIGS. 10(a), (b) and (c) illustrate cross sections taken perpendicular to the axis of thelip 3, andFIGS. 10(a) , (b′) and (c′) show side views along the axial direction of the lip. -
FIGS. 10(a) , (a′), (b) and (b′) illustrate alip 3 formed of two members of thelips FIGS. 10(c) and 10 (c′) illustrate alip 3 formed of three members of thelips FIG. 10 (c′), thelip 3 c has an annular shape, but may be divided into two or more portions on the outer periphery of themandrel 1 as with thelips - Also, each split lip may be integral with the socket or the cone, or may be separate.
- Further, as illustrated in
FIG. 10 (b) , the angle of the parting plane of thelip 3 is not limited and may not necessarily be parallel to the mandrel axis. In the downhole plug including thelip 3 of Embodiment 5, since the length of the portion, in the outer peripheral of themandrel 1, in contact with thecenter element 2 is not constant, the average value thereof is used as (b). - The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention.
- A plug for plugging a wellbore includes: a cylindrical body; an elastic member with annular shape configured to surround an outer peripheral surface of the cylindrical body and to be deformed under pressure; at least one protective member configured to surround the outer peripheral surface of the cylindrical body and to prevent at least a part of the elastic member from coming into contact with the cylindrical body; and a pair of pressure transmission means configured to sandwich the elastic member in an axial direction of the plug and to apply pressure to the elastic member in the axial direction to compress the elastic member, where, when the elastic member is deformed by applying a pressure of 50 MPa to the plug in the axial direction, a ratio (b/a) of an axial length (b) of a part of the elastic member where the cylindrical body and the elastic member are in contact with each other, to a maximum axial length (a) of the elastic member in a cross section along the axial direction is less than 0.5.
- According to this configuration, when pressure is received from one side in the axial direction of the plug, the elastic member sandwiched between a pair of pressure transmission means provided on the outer peripheral surface of the cylindrical body is compressed and deformed via a pair of pressure transmission means provided on the outer peripheral surface of the cylindrical body. At this time, at least a part of the elastic member is prevented from coming into contact with the cylindrical body by the protective member also provided on the outer peripheral surface of the cylindrical body. Specifically, when the elastic member is deformed by applying a pressure of 50 MPa in the axial direction, a ratio (b/a) of a length (b) in the axial direction of a part where the cylindrical body and the elastic member are in contact with each other to a maximum axial length (a) of the elastic member in a cross section along the axial direction is less than 0.5. When the elastic member is compressed and deformed, a force is applied from the elastic member to the cylindrical body. However, since the part where the elastic member and the cylindrical body are in contact with each other falls within the above range, the force applied to the cylindrical body is reduced. As a result, breakage of the cylindrical body can be prevented, and the plug has excellent pressure resistance.
- At least one of the protective members may be integrated with one of the pressure transmission elements constituting the pressure transmission means.
- Further, at least one of the protective members may be independent of the pressure transmission means.
- Further, a plurality of protective members are provided, and one of the plurality of protective members are integrated with one of the pressure transmission elements constituting one of the pair of pressure transmission means, and another one of the plurality of protective members is integrated with one of the pressure transmission elements constituting the other of the pair of pressure transmission means.
- In addition, one of the pressure transmission elements integrated with the protective member is a conical member which is in contact with an end of the elastic member and whose outer diameter increases from an end of the cylindrical body toward the elastic member.
- The protective member may be annular. According to this configuration, the cylindrical body of the plug can be more effectively prevented from coming into contact with the elastic member. Therefore, the plug is excellent in pressure resistance.
- Additionally, the length (b) may be 0. According to this configuration, since the cylindrical body of the plug is not in contact with the elastic member, the plug is further excellent in pressure resistance.
- An embodiment of the present invention will be described below. The present invention is not limited to the examples below, and it goes without saying that various aspects are possible with regard to the details thereof.
- When the center element was deformed by applying a pressure of 50 MPa in the axial direction of the downhole plug, a hydraulic pressure resistance test was performed on a downhole plug in which the ratio (b/a) of the axial length (b) of the part where the mandrel and the center element were in contact with each other to the maximum axial length (a) of the center element in a cross section along the axial direction was 0.
- The downhole plug was placed in a metal tube having an inner diameter that is 1.1 times the outer diameter of the downhole plug, such that the axes of the downhole plug and the tube were parallel. The inside of the cylinder was maintained at 90° C., and a hydraulic pressure of 60 to 63 MPa was applied in the axial direction of the downhole plug to plug the cylinder. Then, the time period during which the tube was kept plugged was measured.
- The results are shown in Table 1.
- The same operation as in Example 1 was performed except that a downhole tool in which the axial length (a) of the center element and the axial length (b) of the part where the mandrel and the center element were in contact with each other in the cross section along the axial direction were equal to each other was used, the temperature was set to 90 to 93° C., and the hydraulic pressure was set to 50 to 53 MPa.
- The same operation as in Example 1 was performed except that a downhole tool in which the axial length (a) of the center element and the axial length (b) of the part where the mandrel and the center element were in contact with each other in the cross section along the axial direction were equal to each other was used, the temperature was set to 90 to 93° C.
-
TABLE 1 Hydraulic Temperature pressure Retention b/a [° C.] [MPa] time Example 1 0 90 60 to 63 24 hours or longer Comparative Example 1 1 90 to 93 50 to 53 6 hr 20 min Comparative Example 2 1 90 to 93 60 to 63 1 hr 55 min -
- 1 Mandrel (Cylindrical body)
- 2 Center element (Elastic member)
- 3, 3 a, 3 b, 3 c Lip (Protective member)
- 4, 4 a, 4 b Socket (Pressure transmission means)
- 5 a, 5 b Cone (Pressure transmission means)
- 6 a, 6 b Slip (Pressure transmission means)
- 7 a, 7 b Ring (Pressure transmission means)
- 8 Load ring (Pressure transmission means)
- 9 Bottom
- 10 Ball
- 11 Partition
- 12 Well wall
- 13 Ball seat
- 20, 21 Downhole plug (Plug)
Claims (9)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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JP2018-069248 | 2018-03-30 | ||
JP2018069248A JP2019178569A (en) | 2018-03-30 | 2018-03-30 | Downhole plug with protective member |
PCT/JP2019/003604 WO2019187622A1 (en) | 2018-03-30 | 2019-02-01 | Downhole plug comprising protection member |
Publications (1)
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US20210108482A1 true US20210108482A1 (en) | 2021-04-15 |
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ID=68058710
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US16/982,102 Pending US20210108482A1 (en) | 2018-03-30 | 2019-02-01 | Downhole plug with protective member |
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US (1) | US20210108482A1 (en) |
JP (1) | JP2019178569A (en) |
CN (1) | CN111801484B (en) |
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GB (1) | GB2587124B (en) |
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US20220389786A1 (en) * | 2021-06-02 | 2022-12-08 | Halliburton Energy Services, Inc. | Sealing assembly for wellbore operations |
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US20170370176A1 (en) * | 2014-04-02 | 2017-12-28 | Magnum Oil Tools International, Ltd. | Split ring sealing assemblies |
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WO2011133810A2 (en) * | 2010-04-23 | 2011-10-27 | Smith International, Inc. | High pressure and high temperature ball seat |
CN202117618U (en) * | 2011-03-31 | 2012-01-18 | 大庆油田有限责任公司 | High temperature and high pressure resistance open hole hook wall packer |
US9103177B2 (en) * | 2011-08-22 | 2015-08-11 | National Boss Hog Energy Services, Llc | Downhole tool and method of use |
CN202325389U (en) * | 2011-10-13 | 2012-07-11 | 中国石油化工股份有限公司 | Top packer for tail pipe |
US9121253B2 (en) * | 2012-12-19 | 2015-09-01 | CNPC USA Corp. | Millable bridge plug system |
CN203130031U (en) * | 2013-02-21 | 2013-08-14 | 沈阳大华测控技术有限公司 | High-pressure hydraulic pressing crack packer |
JP6327946B2 (en) * | 2013-05-31 | 2018-05-23 | 株式会社クレハ | Well drilling plug with mandrel formed from degradable material |
JP6359355B2 (en) * | 2013-12-27 | 2018-07-18 | 株式会社クレハ | Plug for well excavation comprising an annular rubber member that can be expanded and formed from a decomposable rubber material |
CN104074487B (en) * | 2014-07-11 | 2017-01-04 | 中国石油大学(北京) | Drawing type packer |
JP2016160694A (en) * | 2015-03-03 | 2016-09-05 | 株式会社クレハ | Degradable rubber member for downhole took, downhole tool, and well drilling method |
GB2548727B (en) * | 2017-05-19 | 2018-03-28 | Ardyne Tech Limited | Improvements in or relating to well abandonment and slot recovery |
US10760382B2 (en) * | 2017-09-26 | 2020-09-01 | Baker Hughes, A Ge Company, Llc | Inner and outer downhole structures having downlink activation |
-
2018
- 2018-03-30 JP JP2018069248A patent/JP2019178569A/en active Pending
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2019
- 2019-02-01 GB GB2016485.1A patent/GB2587124B/en active Active
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US20170370176A1 (en) * | 2014-04-02 | 2017-12-28 | Magnum Oil Tools International, Ltd. | Split ring sealing assemblies |
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US20220389786A1 (en) * | 2021-06-02 | 2022-12-08 | Halliburton Energy Services, Inc. | Sealing assembly for wellbore operations |
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CA3094937A1 (en) | 2019-10-03 |
GB2587124B (en) | 2022-06-15 |
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CA3094937C (en) | 2023-08-01 |
WO2019187622A1 (en) | 2019-10-03 |
GB202016485D0 (en) | 2020-12-02 |
GB2587124A (en) | 2021-03-17 |
CN111801484A (en) | 2020-10-20 |
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